The objective is to study the mechanisms that regulate growth and differentiation in the intestine. The project describes an analysis of a presently uncharacterized zinc finger protein, named here GKLF, that we have shown is expressed primarily in the gut mucosal layer and in quiescent but not proliferating cells. The aims are to 1) examine the tissue/cellular and subcellular distribution of GKLF by in situ hybridization analysis of tissues and by immunocytochemical analysis of cells expressing endogenous GKLF or epitope-tagged GKLF cDNA, respectively, 2) establish the GKLF protein is a sequence-specific DNA binding transcription factor by identifying the DNA element to which GKLF binds using the Target Detection Assay and testing the ability of GKLF to affect transcription in cotransfection experiments using a reporter gene, and 3) study the effect of GKLF on cell proliferation by overproducing GKLF in 3T3 cells in the presence or absence of GKLF anti- sense RNA and measuring the effect on cell proliferation. The biomedical interest in proteins associated with cell cycle arrest, differentiation, DNA repair and senescence has become increasingly more pronounced as the study of other growth inhibitory genes such as those for p53, retinoblastoma, interferons, transforming growth factor beta, and Gadd have revealed their importance in maintaining the cell in a nontransformed state.